Azeotrope-like mixture of 2-propanol and 1H-perfluorohexane

ABSTRACT

The invention relates to an azeotrope-like mixture which contains about 8-12% by weight of 2-propanol and about 88-92% by weight of 1H-perfluorohexane and to a process for cleaning electronic components, in particular soldered circuit boards or printed circuits, with the aid of this mixture.

It is state of the art to use mixtures of1,1,2-trichloro-1,2,2-trifluoroethane (R 113) and alcohols such asmethanol, ethanol or 2-propanol to clean soldered circuit boards andother electronic components (British Patents 1 026 003 and 1 399,867).U.S. Pat. No. 3,960,746 discloses an azeotrope-like mixture of R 113,methanol and nitromethane for the same purpose. Since, however, CFCs aresuspected of damaging the ozone layer, it is necessary to dispense withthis class of substances.

Various water-based systems and systems based on non-halogenated organicsolvents are currently under discussion for the electronics industrysector, in particular for cleaning circuit boards after the solderingoperation. However, it is difficult to find the correctsurfactant/complex-forming agent combination in the case of aqueouscleaning agents. The system must also be adapted to the mechanicaltreatment, such as rinsing, brushing steam jet or ultrasonic treatment.Aqueous cleaning systems are frequently ruled out in the case of SMT(Surface Mount Technology), since the water can be removed again onlywith difficulty.

When non-halogenated organic solvents, such as petroleum spirit,alcohols, terpenes or esters, are used the installation must be ofexplosion-proof design because of the combustibility and the explosivenature of the substances and, therefore, on economic grounds use of saidsolvents in surface treatment installations is worth considering only ina few cases.

Azeotrope-like solvent mixtures of 1,4-dihydroperfluorobutane andmethanol and, respectively, of 2,2,2-trifluoroethyl1,1,2,2-tetrafluoroethyl ether and ethanol, which are suitable forcleaning electrical and electronic components, are described in GermanPatent Applications P 4 002 120.3 and P 4 013 369.9, which have notpreviously been published.

Surprisingly, it has now been found that 1H-perfluorohexane CF₃ --(CF₂)₄--CF₂ H forms an azeotrope-like solvent mixture with 2-propanol, whichmixture is outstandingly suitable for cleaning electronic components,especially soldered circuit boards or printed circuits, in particularfor removing soldering fluxes.

The invention relates to an azeotrope-like mixture which contains about8-12% by weight of 2-propanol and about 88-92% by weight of1H-perfluorohexane. Preferably the mixture contains 8.5-11.0% by weightof 2-propanol and in particular 9.0-10.0% by weight of 2-propanol, theremainder being 1H-perfluorohexane in each case. The invention alsorelates to a process for cleaning electronic components, in particularsoldered circuit boards or printed circuits, wherein the components arewashed with an azeotrope-like mixture which contains about 8-12% byweight of 2-propanol and 88-92% by weight of 1H-perfluorohexane.Preferably, a mixture which contains 8.5-11.0% by weight of 2-propanoland in particular 9.0-10.0% by weight of 2-propanol is used, theremainder being essentially 1H-perfluorohexane in each case.

A particularly preferred solvent mixture contains 90.7% by weight of1H-perfluorohexane and 9.3% by weight of 2-propanol and has a boilingpoint under 1 bar of 63.4° C.

In the case of the mixture, according to the invention, of 2-propanoland 1H-perfluorohexane, the composition of the vapor is identical orsubstantially identical to the composition of the liquid, that is to saythe composition of the mixture does not change or does not changesubstantially on vaporization. The solvent mixture according to theinvention has the further advantage that it contains no chlorine andthus causes no ozone damage. Moreover, it is not combustible and can beused in the conventional ultrasonic, dip and brush wash installations.

EXAMPLE 1

A glass fiber-reinforced base material for circuit boards based onpolyester was coated with a commercially available soldering flux (ZevaC 20-200 from Zevatron; main constituent colophony, with additionalactivators) and dried for 18 hours at 60° C. in an oven. The materialwas then washed with a mixture of 1H-perfluorohexane (90.7% by weight)and 2-propanol (9.3% by weight) using ultrasound. The period of actionwas 30-60 seconds; the flux was completely removed.

EXAMPLE 2

The procedure was as in Example 1 except that a different soldering fluxwas used (Zeva C 30-300 from Zevatron), which again contained colophonyas the main constituent in addition to activators. After a period ofaction of 30-60 seconds, the flux was completely removed. In the case ofthe conventional mixtures of 1,1,2-tri-chloro-1,2,2-trifluoroethane withmethanol, ethanol or 2-propanol, on the other hand, the treatment timesare between 60 and 90 seconds, depending on the flux. Moreover, ionicresidues can be better removed with the azeotrope than with theconventional mixtures.

EXAMPLE 3

Example 3 was carried out in the same way as Example 1 except that theflux used was GR8 flux from Ersa (main constituent colophony, withadditional activators). After a period of action of 30-60 seconds theflux was completely removed.

We claim:
 1. An azeotrope-like mixture consisting essentially of 8-12%by weight of 2-propanol and 88-92% by weight of 1H-perfluorohexane, saidmixture having a boiling point at 1 bar of about 63° C. and wherein thecomposition of said mixture does not substantially change uponevaporation.
 2. The azeotrope-like mixture as claimed in claim 1, whichconsists essentially of 8.5-11.0% by weight of 2-propanol and 89.0-91.5%by weight of 1H-perfluorohexane.
 3. The azeotrope-like mixture asclaimed in claim 1, which consists essentially of 9.0-10.0% by weight of2-propanol and 90.0-91.0% by weight of 1H-perfluorohexane.
 4. A processfor cleaning electronic components which comprises washing thecomponents with an azeotrope-like mixture as claimed in claim
 1. 5. Aprocess for removing soldering fluxes, which comprises washing thesoldering fluxes with an azeotrope-like mixture as claimed in claim 1.6. The process as claimed in claim 4, wherein the electronic componentsare soldered circuit boards or printed circuits.